When I had my 2002 CTD I never changed my oil. At 3,000 miles I made the switch to AMSOIL and added the Dual Remote Filtration System. I backed it up with oil analysis, and when I traded it in with a little over 70,000 miles on it and 5 years the oil report showed the oil was suitable for continued use. Just changed my filters when needed and topped off.

Changed the oil and filter yesterday....too wet to ride but warm enough to work refilled the crankcase with 3 gallons 15W40 Royal Purple and I Fleetguard LF16035...black on start up. Oh well.

JFJ, how often you change the royal purple?

It just baffles me that my 07, 6.7 is still clean and the 09, 6.7 is immediately black.

I'm sure somebody has, but what would oil analysis show on dino oil like Rotella as far as oil change recommendations?

I check it every day I haul before startup along with the radiator.
Had 15K miles on it this time and hadn't added a drop.
But I do start it in the morning and it runs till we're back home unless we stop for supper somewhere.
I also add 1 qt of mobile 1 synthetic, making my own synthetic blend since a gallon of "blend" can be as low as 5%.
390K miles and working hard every day. Must be liking it.

This oil change interval was 14 months and 14,200 miles. I got started on RP 15W40 when one of the local chain stores had it, nobody was buying it at 30.00 a gallon so they pulled it and was sending it back....I asked about it and they said if I wanted it I could buy it fir 10.00 a gallon....bought 17 gallons. Been on it ever since. Usually once a year or 14-15k.